1. Field of the Invention
The present invention relates to a communication system, and more particularly, to a method for processing signal in communication system having plurality antennas.
2. Background of the Related Art
In general, in a radio communication, a received signal includes a desired signal (hereafter called as ‘original signal’) as well as interferential signals, wherein there are in general a plurality of interferential signals for one original signal. Since an extent of a communication distortion caused by the interferential signals is fixed by a sum of an original signal power and all interferential signal powers, even if a level of the original signal is significantly higher than each of the levels of the interferential signals, the communication distortion may be occurred if a number of the interferential signals are great, to make a total power of the interferential signals great. FIG. 1 illustrates a related art method for forming a beam in an array antenna system.
Referring to FIG. 1, the related art array antenna system using method for CDMA (code division multiple access) type radio link is provided with a frequency down converter 101 for converting a very high frequency signal received at an antenna to a base band signal, an analog to digital converter 102 for digitizing the base band signal, a first multiplier 103 for despreading the digital signal, an integrator 104, a second multiplier 105 for applying a weight vector to a desired signal to obtain a greater gain of the desired signal, a beam former 106 for spatial processing of the desired signal, and an array forwarder 107 for synthesizing, and forwarding the signals having the weight vectors applied thereto.
A related art method for forming a beam of the foregoing array antenna will be explained.
The frequency down converter 101 converts a signal received through each antenna element into a baseband analog signal, which is then digitized at the analog to digital converter 102. The first multiplier 103 and the integrator 104 despread the digitized signal and extract only a desired signal therefrom. The second multiplier 105 applies a weight vector to the extracted signal. The signals having the weight vectors applied thereto are synthesized at the array forwarder 107, and forwarded to a demodulator (not shown). The weight vector provided by the beam former 106, which renews the weight vector from output signals of the analog to digital converter 102 and output signals of the integrator 104. The output signals from the analog to digital converter 102 are high rate signals before being despread in a code the CDMA system knows already, and the output signals from the integrator 104 are low rate signals after being despread in a code the CDMA system knows already.
In the related art, an autocovariance matrix of signals sampled from the signals before being despread is calculated, an autocovariance matrix of signals sampled from the signals after being despread is calculated, and the weight vector for the spatial processing is calculated from the matrices.
However, the adaptive algorithm for the adaptive array antenna in the related art requires altering a generalized eigenvalue problem to an eigenvalue problem of only one matrix. In the altering process, it is required to divide one of two matrices in the generalized eigenvalue problem into two matrices again by utilizing that the matrices in the generalized eigenvalue problem are ‘positive definite’ matrices, and to obtain inverse matrices of the two divided matrices, which is cumbersome, and not suitable for use as a real time adaptive array algorithm due to too much calculation required.